The use of agent based services in a Computational Grid is outlined—along with particular roles that these agents undertake. Reasons why agents provide the most natural abstraction for managing and supporting Grid services is also discussed. Agent services are divided into two broad categories: (1) infrastructure services, and (2) application services. Infrastructure services are provided by existing Grid management systems, such as Globus and Legion, and application services by intelligent agents. Usage scenarios are provided to demonstrate the concepts involved.